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"There was also a strange Elf clad in green and brown, Legolas, a messenger from his father, Thranduil, the King of the Elves of Northern Mirkwood." - Book II, The Lord of the Rings: The Fellowship of the Ring

"Legolas had a bow and a quiver, and at his belt a long white knife." -Book II, The Lord of the Rings: The Fellowship of the Ring

"...(Legolas) had no boots, but wore only light shoes, as he always did, and his feet made little imprint on the snow." -Book II, The Lord of the Rings: The Fellowship of the Ring

"But Legolas stood beside him, shading his bright elven eyes with his long slender hand." - The Lord of the Rings: The Two Towers

"...for Legolas was fair of face beyond the measure of Men..." -The Lord of the Rings: The Return of the King

"He was tall as a young tree, lithe, immensely strong, able swiftly to draw a great war-bow and shoot down a Nazgûl, endowed with the tremendous vitality of Elvish bodies, so hard and resistant to hurt that he went only in light shoes over rock or through snow, the most tireless of all the fellowship."Ch VI The History of Eriol, The Book of Lost Tales 2

[Tolkien did not supply a birthdate or age for Legolas, but the following quotes suggest that he is at least five hundred years old:]

[Said Gandalf,] 'Behold! we are come to the great barrows where the sires of Théoden sleep.'

'Seven mounds upon the left, and nine upon the right,' said Aragorn. 'Many long lives of men it is since the golden hall was built.'

'Five hundred times have the red leaves fallen in Mirkwood in my home since then,' said Legolas, 'and but a little while does that seem to us.'

The Two Towers, LoTR Book 3, Ch 6, The King of the Golden Hall

They rode in silence for a while; but Legolas was ever glancing from side to side, and would often have halted to listen to the sounds of the wood, if Gimli had allowed it.

'These are the strangest trees that ever I saw,' he said; 'and I have seen many an oak grow from acorn to ruinous age. I wish that there were leisure now to walk among them: they have voices, and in time I might come to understand their thought.'